The present invention relates to electrical test instruments and, in particular, to a switch matrix for test connections.
Referring to FIG. 1, a typical cross-point switch matrix 10 is formed from rows and columns of output lines Oi and input lines Ii, respectively. “Switches” 12 are located at the cross points to allow connection of inputs to outputs. The switches may be, for example, simple mechanical switches, mechanical relays, or solid-state electronic equivalents thereto.
One limitation on the operation of the switch matrix 10 is that the upper frequency limit is affected by the “stub” lengths in the switch matrix 10. A stub may be considered to be a conductor connected to a signal of interest, but not actually carrying the signal from input to output. For example, when the input IN is connected to the output Oi, stubs include the conductor portion 14 and conductor portion 16. In general, as the number of elements in the switch matrix 10 increases, the stub effects increase, limiting the frequency of the signal that may be switched.